Heat oil in a large pot over medium heat until hot. Add corn kernels until 2 to 3 pop; stir in white and brown sugars. Cover pot with a lid; agitate pot in a circular motion on the stove. Allow corn to pop, agitating pot constantly, until popping rate slows down to 1 pop every 2 to 3 seconds. Remove pot from the stove; shake pot until popping stops. Transfer popcorn to a large bowl; cool to room temperature. Break apart large popcorn clumps by hand; season with salt.